Indene has been used in the preparation of synthetic resins, e.g., coumarone-indene resins, but more recently has found use as a comonomer in other resins and, in high purity, as a monomer to improve the surface properties of polymers with minimal loss to vaporization by virtue of its high vapor pressure.
Previous methods for obtaining high purity indene include centrifugation, distillation and crystallization of indene-rich naphtha-cracker pyrolysis oil.
A number of publications exist which relate to removal of impurities from various petroleum fractions, e.g., naphtha, naphthalene, etc. These references indicate group selectivity for a number of impurities including indene, but are not highly selective for indene alone. Furthermore, they do not teach any means for recovering indene from the adsorbent. In the present invention, the selection of a desorbent to recover indene alone is an important step in that it is necessary to remove other less strongly adsorbed feed components before desorbing indene. For example, reference is made to: Jean et al. Preprint Papers A. Chem. Soc., Div Fuel Chem. 32 (3), 262-5 (CA 105 (12): 100117y); Kondratov et al. Zh. Fiz. Khim., 50(3), 801 (CA 84 (24): 170137b); Kondratov et al., Koks Khim. (9) 39-43 (CA 90 (5): 38709j).
An article by Vykhristyuk et al., Koks Khim. (2) 38-41 (CA 94: 208588w) discloses the removal of a number of impurities from naphthalene by treating with NaX zeolite adsorbent. Again, the authors are interested in removing small amounts of all types of impurities from a fuel and do not deal with recovering the impurities or with recovering indene from the remaining contaminants.
It is an object of this invention, however, to obtain indene in highly purified form by highly selective chromatographic adsorption separation process from mixtures, including petrochemicals, such as crude oil fractions, e.g., naphtha, naphthalene; processed mixtures, e.g., naphtha cracker pyrolysis oil; synthetically-produced mixtures, e.g., dehydrogenation or cyclization reactions containing aromatics, etc., which cannot be separated easily and economically by other conventional means.
It is a further object to provide a desorbent which will selectively desorb the indene from the adsorbent with sufficient resolution so as to obtain indene product with substantially reduced impurities and other feed materials. The preferred desorbent is toluene, but benzene and fluorobenzene and other liquid alkyl- or halogen-substituted monocyclic aromatics are suitable for use in the process.
It is further believed that the crystallization process described previously could be much more efficient and economical if the product of this invention were used as the feed material, thereby reducing the overall cost of achieving very high purity indene.